一种不完全补偿机器人标定方法

为了避免修改影响机器人逆运动学模型的参数,分析了绝对定位误差的主要来源,以及标定需要保证的前提条件。在此基础上介绍了一种标定方法,该方法利用三坐标测量仪对机器人六个关节分别进行测量,生成六组点云,对每组点云采用最小二乘法拟合平面及圆。根据D-H参数的定义,计算出容易补偿的各参数实际值,并依据计算结果对参数进行了补偿。通过实验证明,该方法有效提高了绝对定位精度,使精度能够满足实际工程需要,而且操作简单方便,实用性强。     

基于内点法实现关节式坐标测量机参数标定

提出一种基于内点法的关节式坐标测量机参数自标定方法。首先,基于D-H方法,建立关节式坐标测量机的运动学模型,在此基础上建立参数误差模型。利用自制标定块,采用多位姿测量多点的方法获得标定用数据,从而使该标定方法能够在现场应用;以测量机的长度测量精度为基础建立目标函数,利用内点法进行参数辨识,该算法对迭代初值无要求,可有效提高参数标定成功率。通过标定实验得到坐标测量机的运动学参数,验证了该方法的可行性。经过标定后,关节式坐标测量机的单点重复性精度和长度测量精度分别提高了93.65倍和100.13倍。     

利用激光跟踪仪对机器人进行标定的方法

提出一种简单的利用激光跟踪仪和线性方程最小二乘解对机器人进行标定的方法。通过将机器人运动学方程线性化,建立机器人末端凸缘盘位置误差与连杆D-H参数误差的关系方程。利用激光跟踪仪确定机器人的基坐标系,并通过圆周法求解每个关节电动机的直线方程,进而可以求得机器人的连杆扭角。通过激光跟踪仪测量机器人目标点的坐标值,并通过串口获得机器人6根轴的角度值建立标定方程。通过求解此方程,获得机器人的实际D-H参数,并将此参数应用于修正系统的运动学模型,能够提高机器人的绝对精度。最后对解算过程中的误差和原因进行说明,并对机器人的误差原因进行分析,指出标定过程中需要注意和改进的几个问题。     

基于三坐标测量机的球面5R并联机构运动学标定研究

基于D-H参数建立了包含球面5R并联机构全部结构参数的标定用位置反解模型。建立了该机构位置和姿态运动学标定模型,结合实际样机进一步得到了标定简化模型,简化了参数辨识与补偿计算过程。通过三坐标测量机确定了球面机构的近似球心,并以此为原点建立了测量坐标系,从而实现了测量参考系与运动参考系的统一,便于末端执行器位姿的测量。通过标定实验,验证了该方法能够提高球面并联机构的绝对精度。     

类CNC特性的机器人加工装备研究与应用

依次旋转机器人的每个轴获得其轴线方程,利用代数法求取机器人的D-H参数以及零位误差,实现机器人几何参数的标定。将标定后的机器人作为测量工具,测量装备中各单元相对机器人的转换矩阵,并用测量的矩阵调整CAM软件中对应单元模型的位姿,实现加工空间与CAM空间的配准。借助CAM软件产生刀轨迹,利用配准的参数、实际机器人逆运动学方程以及零位误差,对刀轨迹进行后处理,产生机器人加工轨迹。实现了几何参数标定、加工装备标定以及软件自动编程的机器人加工装备具有类似CNC加工装备的特性,不仅具有高的加工精度而且易于操控,其实验加工的平均误差不超过0.7 mm。     

基于距离误差的服务机器人运动学参数标定研究

基于MDH(Modified Denavit-Hartenberg)模型,建立自主研发的服务机器人单个关节误差模型,用空间两点间的距离误差衡量机器人的绝对定位精度,并结合建立的单关节误差模型,推导了基于距离误差的运动学标定模型。运用该标定模型不仅可以简化测量过程,还可以避免测量系统与机器人系统之间的坐标转换,从而提高测量精度。最后,结合服务机器人部分解耦的结构特征来制定实验测量点的选取方案,并使用三坐标测量机测量其末端位置。实验结果表明,机器人的绝对定位精度得到明显提高。     

基于病态参数分离的机器人运动学标定测量构型优化

针对一种高灵巧性机器人及其连杆参数高敏感性与高定位精度需求,为解决机器人运动学标定随机测量构型存在绝对 定位精度低、参数辨识效果及标定结果鲁棒性较差的问题,提出一种病态参数分离与 DETMAX-改进差分进化(DETMAX-IDE) 算法的机器人运动学标定测量构型分步优化方法。 首先,建立机器人位置误差模型。 其次,建立一种可观性综合指标,评价不 同机器人标定测量构型的总体可观测性和灵敏度。 最后,分离机器人运动学位置误差模型的病态参数,建立测量构型优化目标 函数和约束条件,提出一种基于 DETMAX 算法与改进差分进化算法结合的分步迭代优化算法(简称为 DETMAX-改进差分进化 算法,简写为 DETMAX-IDE 算法),开展机器人运动学标定测量构型分步迭代优化。 通过机器人运动学标定仿真与实验,验证 了所提方法的有效性。 实验结果表明,与随机测量构型相比,所提方法对应的机器人绝对定位精度的平均值和均方差分别降低 了 62. 09% 和 62. 45% 。     

基于PSO算法的工业机器人绝对距离自标定方法

为了提高工业机器人的定位精度,提出一种自标定算法,首先采用D-H参数模型对机器人进行建模,分析并建立D-H参数误差与机器人末端误差的函数,再设计一个可旋转的标定平台,使机器人去探测不同位姿下的标定平台上的两个标定点,最后采用PSO算法对不同位姿下标定平台两点间的绝对距离来实现对机器人D-H参数误差的辨识。该方法标定过程简单,数据获取方便,并且不依赖于高精度测量仪器。经实验证明,标定后位置精度提高了10倍以上,均方根误差相较于标定前有数量级上的提升,说明机器人标定后,各项误差与机器人实际误差高度一致,从而保障了机器人工作过程的精确性。     

工业机器人误差补偿及冗余参数研究

针对现有工业机器人定位精度较低,提出了通过机器人运动学标定对误差进行补偿的方法。基于D-H运动学模型和微分变换法建立机器人位姿误差模型,然后对误差模型进行冗余参数分析,消除冗余参数得到可辨识的线性方程,最后用迭代最小二乘法进行求解,修正几何参数进而提高机器人定位精度。通过在自主研发的机器人上试验验证,该方法补偿效果明显,增加了参数辨识的准确性和鲁棒性,为机器人标定技术的发展奠定了一定的基础。     

一种脑外科手术机器人运动学参数标定方法

为提高脑外科手术机器人绝对定位精度,提出了一种串联式六自由度手术机器人运动学参数标定方法。根据脑外科手术机器人应用环境,采用一种针对手术工作空间的机器人参数采集方式,通过非支配排序的带有精英策略的多目标优化算法(NSGA-Ⅱ),将运动学模型标定问题转换为基于距离误差的多目标优化问题进行计算。通过模拟手术环境完成机器人参数标定的测试实验,说明利用这种标定方法可有效降低手术机器人系统绝对定位误差(误差降低了75%),提高机器人局部工作区域的定位精度。     

Ball array calibration on a coordinate measuring machine using a gage block

The distances between the balls of a ball array used in machine geometry calibration have to be very accurate. These distances can be calibrated using a laser measurement system, which requires specially designed optical devices and measuring probes. In this paper, a new and economical alternative method for calibrating the ball array is described. A single gage block is used for measuring the standard distance at the starting position. Then, the exact distances between the balls can be obtained by using the coordinate measuring machine (CMM) probe motion. This method does not depend on the accuracy of the CMM. Also, this method does not require expensive instruments or devices, but a CMM and a gage block. A simple “parallel-plane” bracket, mounted on to the measuring end of a CMM probe, is used to determine the centers of the balls automatically and accurately.     

Enhance performance of inspection process on Coordinate Measuring Machine

Coordinate Measuring Machine (CMM) has been an important inspection tool in quality control for several years owing to its high accuracy and precision. Effectiveness of inspection plan generated by CMM greatly depends on measurement cycle time. Lesser the inspection time taken by CMM to measure a given part better will be the performance of inspection process. Therefore, it has been critical to reduce measurement time for efficient performance of inspection process. In this paper, methodologies to generate most suitable measurement path resulting into minimum inspection time has been introduced. These methodologies are based on different algorithms to reduce measurement cycle time for CMM. The different algorithms have successfully been explored and compared to show their effectiveness in minimizing inspection time for stationary CMM equipped with touch trigger probe. The proposed methodologies have also been implemented and tested on real-world mechanical part with certain number of features to demonstrate their applicability.     

激光制导测量机器人系统设计及运动学分析

提出新型“光束运动—光靶跟踪”激光跟踪测量方法,并在此方法基础上研究激光制导测量机器人技术,研制并开发一种能够在水平和垂直被测对象表面上运动的小型轮臂复合式激光制导测量机器人系统。该机器人机构融合轮式机构、爬行臂式结构和真空吸附式机构的优点,具有重量轻、体积小、运动灵活和反应快速等特点,可以根据不同被测对象表面特征变换测量模式,利用轮式结构实现机器人在水平被测表面上高速远距离运动,利用爬行臂式和真空吸附式机构实现机器人在倾斜光滑表面上灵活地爬行和转向。建立机器人的运动学模型并对其运动特性进行分析,利用激光跟踪仪和三坐标测量机对研制激光制导测量机器人进行性能测试,试验结果不仅证明了该机器人能够跟踪激光束自动高效地完成被测对象实体测量,同时也验证了所建模型的有效性和正确性。     

Measuring external profiles of porous objects using CMM

Coordinate measuring machine (CMM) has been extensively used in surface measurement and inspection. CMM produces more accurate and reliable results compared with non-contact measurement devices, since CMM measures target surfaces in a tactile way and is not affected by surface reflection quality. However, when there is porosity on the outside surfaces, CMM measurement will have errors because part of the probing stylus will come into the porosity spaces. This paper presents a method of using CMM to measure external profiles of objects with external porosity spaces. The center of a CMM probing stylus will be compensated to avoid porosity spaces and located above external surface areas along surface normal directions. Such a probing strategy can be implemented in both computer-aided design (CAD)-guided mode and non-CAD-guided mode. When the CAD model is available, the probing styli are guided to approach the surface along its normal directions successively to identify and avoid porosity spaces. When the CAD model is unavailable, surface normal directions will be estimated first and then adjusted. The presented method is able to avoid porosity spaces in CMM measurement regardless of the availability of CAD models.     

Evaluation of a multi-sensor horizontal dual arm Coordinate Measuring Machine for automotive dimensional inspection

Multi-sensor coordinate measuring machines (CMM) have a potential performance advantage over existing CMM systems by offering the accuracy of a touch trigger probe with the speed of a laser scanner. Before these systems can be used, it is important that both random and systematic errors are evaluated within the context of its intended application. At present, the performance of a multi-sensor CMM, particularly of the laser scanner, has not been evaluated within an automotive environment. This study used a full-scale CNC machined physical representation of a sheet metal vehicle body to evaluate the measurement agreement and repeatability of critical surface points using a multi-sensor horizontal dual arm CMM. It was found that there were errors between CMM arms and with regard to part coordinate frame construction when using the different probing systems. However, the most significant effect upon measurement error was the spatial location of the surface feature. Therefore, for each feature on an automotive assembly, measurement agreement and repeatability has to be individually determined to access its acceptability for measurement with a laser scanner to improve CMM utilisation, or whether the accuracy of a touch trigger probe is required.     

Thermo-mechanical analysis in pulsed laser cladding of WC powder on Inconel 718

The increasing interest towards intelligent systems has led to a demand for the development of zero-defect strategies, with a paradigm shift from off-line and dedicated to in-line metrology with integrated robotic systems. However, a major barrier preventing the systematic uptake of in-line metrology is the lack of evaluation of system capability in terms of accuracy, repeatability and measurement time, when compared to the well-established coordinate measuring machine (CMM). In this study, a robotic Laser Radar (LR) solution is assessed in the context of automotive dimensional inspection of Body-In-White (BIW) applications. The objective is both to understand the effect of robot re-positioning error on measurement accuracy and repeatability and to compare measurement results against a CMM. Eighty-one surface points, six edge points, twenty-five holes and sixteen slots were selected from an industry standard measurement plan. Whilst LR exhibits a lower measurement accuracy than twin-column CMM, its repeatability is well within the specification limits for body shell quality inspection. Therefore, as a real-time in-line metrology tool, it is a genuine prospect to exploit. This research makes a significant contribution toward in-line metrology for dimensional inspection, for automotive application, for rapid detection and for correction of assembly defects in real time, with subsequent reduction of scrap and number of repairs/re-works.     

激光制导测量机器人几何误差分析

目的: 为了实现对工件进行自动高效地测量,建立了激光制导测量机器人系统,研制了测量机器人样机。对测量机器人的光靶自动跟踪装置旋转轴偏心误差和光靶与两轮中心连线误差进行了研究。方法:首先,介绍了基于“光束运动-光靶跟踪”理论的激光制导测量机器人技术和原理。接着,根据系统原理,研制了实验样机,并给出其理想的几何关系。然后,推出了旋转轴偏心误差和光靶与两轮中心连线误差几何误差数学模型。最后,利用三坐标测量机与激光制导测量机器人系统对样机进行了比对实验。结果：实验结果表明：光靶中心偏离理想位置的误差（x轴）为0.13mm。结论：对激光制导测量机器人移动反馈控制系统的设计和实现具有指导性作用。     

CMM uncertainty analysis with factorial design

The purpose of this research is to present a method to estimate the Coordinate Measuring Machine (CMM) measurement uncertainty. The approach is based on a performance test using a ball bar gauge and a factorial design technique. A factorial design was applied to carry out a performance test and to investigate CMM errors associated to orientation and length in the work volume. The CMM measurement uncertainty was estimated with components of variance obtained after statistical analysis of variance applied to volumetric measurement errors. An application was performed with a Moving Bridge CMM and the results were compared to the volumetric performance test proposed by ANSI/ASME B89.4.1 standard. The results showed that the proposed method is suitable to investigate CMM hardware performance and determine the contribution of machine variables to measurement uncertainty.     

Training in coordinate measurement using 3D virtual instruments

Coordinate metrology is a subject that has evolved driven by two important vectors: hardware and software development. At present, most 3D measuring software offer features for offline programming of the Coordinate Measuring Machines (CMM). A few software solutions enable the simulation of both the CMM and other elements involved in the measuring process, such as the human operator or an automated system for loading and unloading the measured parts. The paper presents the features and advantages offered by Delmia V5 for simulating a complete measuring environment encompassing: the CMM, the human operator, a robot or automated system for manipulating the parts. The simulations developed represent a powerful learning tool that can complement existing models for CMM training.     

Standardised Reference Data Sets Generation for Coordinate Measuring Machine (CMM) Software Assessment

Rapid and accurate in-process measurement has recently become more common in product cycles, especially for producing parts having 3D contoured shapes. As a result, the ability to analyse large quantities of dimensional data requires today’s coordinate measuring machines (CMM) to employ their extreme functionality. With the increasing demand for performance of the software supplied for a CMM, the testing methods for these software packages must be rigorous, stable, and efficient. Motivated by the aforementioned demand, this work is intended to design and develop an algorithm and computer code to generate the reference data sets representing the coordinates of Gaussian associated features for CMM measured parts. These reference data sets can be used to test the CMM software submitted for approval to the National Institute of Standards and Technology (NIST). A generic algorithm for the development of the data sets is proposed and the program code is designed and developed by employing object oriented concepts. Dynamic errors during measurement are also accounted for, using Fourier harmonics representing the form errors and noise in the measured data. The data sets, being an integral part of the proposed International Standard – ISO 10360, will become a significant step towards the standardisation of software testing procedures for coordinate measuring machines.